Dental instrument for optimal positioning of an X-ray film support

ABSTRACT

A bite block integral with an X-ray film support and extending generally at right angles to the X-ray film support to one side thereof, is formed of upper and lower flat plate portions, one which is integral with the film support, with the other being spaced from said one flat plate portion, normally parallel thereto and connected thereto by means permitting pivoting of the upper plate portion relative to the second about an axis perpendicular to the plane of bite, when positioned in the mouth of the patient between upper and lower tooth rows. An integral bridge may form the pivot axis for the upper and lower plate portions, a rotatable sleeve may effect such pivot connection with the sleeve being shiftable laterally between the upper and lower plate portions. Rectangular block wings may be detachably mounted to respective sides of the bite block plate portions via flanges which are inserted within the gap between the plates to respective sides of the pivot axis between the plates for the bite block.

BACKGROUND OF THE INVENTION

The present invention relates to a dental instrument comprising an X-rayfilm support connected to a bite block and, preferably, also an aligningrod. In prior art instruments of the type above defined the bite blockis homogeneous and its top surface is parallel to its bottom. When apatient opens his mouth, the lower jaw swings around the jaw-joints.This means that an arbitrary point on the lower jaw substantially movesalong a circular arc the radius of which equals the distance of thepoint from an axis through the jaw-joints. Consequently, the fartherback the bite block has to be located, the greater will be the apertureangle of the jaws. It follows that, when a bite block has been insertedbetween the upper and lower tooth rows of a patient and the latter has,obeying the instructions of his dentist, again closed his mouth, onlythe rearmost teeth will contact the bite block whereas a verticaldistance will be left between the block and the upper or lower teeth atthe front edge of the block. The lack of contact between the bite blockand all teeth overlying it means that it assumes an unstable positionand may easily move in response to variations of the bite pressureexerted by a patient. Such movements lead to a displacement of the filmsupport and hence of the film. As is understood, such a swingingmovement of the bite block can occur both around an axis parallel tothat of the jaw-joints and along a horizontal axis parallel thereto.

The instability problem above referred to is aggravated in the followingtwo situations. The one situation is when the rearmost molars are to beX-rayed. In order for the bite block to be received between the teeththe patient then has to open his mouth that much that the only contactbetween the teeth and the bite block will be at the rear edge of thelatter. The second situation is when one or more teeth are missing, sothat even when the frontal teeth are to be X-rayed the bite block doesnot get sufficient support.

The X-raying of the frontal teeth involves a further difficulty. Due tothe anatomy of the palate, the film, and consequently also the filmsupport, will be pressed downwards which often leads to exclusion fromthe picture of the tissue regions around the teeth roots. When thefrontal teeth of the lower jaw are X-rayed the tongue of the patientcauses corresponding problems. For that reason conventional filmsupports can normally not be used in these regions.

The main object of the invention is to provide a dental instrument inwhich the problems above referred to are eliminated, meaning that oncethe patient has pressed his teeth against the bite block the latter willsecurely be retained in the position selected by the dentist.

Other objects and advantages of the invention will appear from thedescription and the drawings which illustrate three differentembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an instrument according to thefirst embodiment.

FIG. 2 is a cross-section taken along line II--II in FIG. 1.

FIG. 3 is a perspective view showing an instrument according to a secondembodiment.

FIG. 4 shows the instrument of FIG. 3 in a lateral view.

FIG. 5 is a perspective view illustrating the third embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS

The instrument shown in FIGS. 1 and 2 substantially consists of a filmsupport 1 with a groove or recess 2 for the film 3. Film support 1 isintegral with a bite block. The device sofar described represents priorart. However, according to the present invention, the bite blockconsists of two generally flat plate portions, hereinafter referred toas the upper portion 4 and the lower portion 5. The lower portion 5 isintegral with the film support. Between block portions 4 and 5 there isa shallow gap. Further, upper portion 4 and lower portion 5 are spacedfrom each other except centrally, where they are interconnected via athin bridge portion 6. In the embodiment shown in FIGS. 1 and 2 filmsupport 1, the lower block portion 5, bridge 6 and the upper portion 4form an integral unit. However, block portion 4 is not connected tosupport 1 at its inner end--to the left in FIG. 1.

The operation of the instrument above described is as follows. Thenarrow bridge 6 serves as a pivot, i.e. the two portions of the biteblock may turn around it and, as has been indicated in FIG. 2, thecorresponding angle is substantial. When a bite block according to theinvention is introduced between the tooth rows of a patient and thelatter bites into the block the two portions thereof will automaticallyassume such angular positions that each of them is parallel with a planethrough the chewing surfaces of the adjacent tooth row or, in otherwords, each tooth row will in at least two points contact the adjacentbite block portion. Consequently, instead of the instable mountingposition which, as has been explained above, exists in prior artinstruments the film will be retained in the position selected by thedentist before he leaves the patient during the film exposure. Thecorresponding advantage has several aspects. Naturally, the primaryaspect is that the dentist knows that the region he intends to X-raywill appear on the film. This avoids the need for repetitions of anygiven exposure. It should be appreciated that such repetitions are notonly time-consuming and costly but that, in addition thereto, mostpatients find them irritating and embarrassing. A second consequence ofthe stable positioning of the film is a protection against movementswhich yields sharp and clear pictures.

In the embodiment according to FIGS. 1 and 2 at the end of bridge 6remote from film support 1 there is a sleeve 7 adapted to receive analigning rod 8.

In FIG. 1 the instrument has been shown in the position it would assumeduring X-raying of teeth in the lower jaw. When teeth or tissues in theupper jaw are to be X-rayed, the instrument is rotated by 180 degrees sothat the film 3 will instead be directed upwards.

There are two differences between the embodiment shown in FIGS. 3 and 4and the one sofar described.

The one difference is that the film support 1 has two grooves 2 and 2aadapted to receive the film 3. As was the case in FIG. 1, groove 2 islocated in a plane perpendicular to planes through the top and bottomsurfaces of the bite block. In contrast thereto, groove 2a is obliquelyoriented relative to the first-mentioned plane. This means that, whengroove 2a receives an X-ray film, the vertical distance between theupper and lower edges of the film will be reduced which is advantageouswhen due to the anatomy conditions it is difficult to accommodate a filmhaving a greater height. Knowing the angle between grooves 2 and 2a thedentist may compensate for that angle by setting up the X-ray camera sothat its focal axis will form the same angle with the aligning rod 8.

The second difference is that sleeve 7 is not integral with the biteblock. Instead, the two portions 4 and 5 of the bite block do at theirfree edges opposite the film support have flanges 9 and 10 engagingcorresponding grooves in sleeve 7. This arrangement makes it possiblelaterally to move the sleeve along said flanges. Further there is nocounterpart to bridge portion 6 in FIG. 2 meaning that the movable blockportion 4 is connected to sleeve 7 only. Consequently, when sleeve 7 isin an extreme position as shown in FIG. 3, the turning axis will belocated at the one side of the block instead of centrally. Thecorresponding advantage is that the film can be brought into positionsdeeper back into the mouth than is possible when the aligning rod iscentrally located which is valuable when the rearmost molars are to beX-rayed.

The instrument shown in FIG. 5 has been supplemented with wing-likelateral pieces 11 and 12 which may detachably be connected to bite block4, 5. They extend the bite block in the direction of the tooth row whichis of special value when front teeth are to be X-rayed. This is due tothe fact that the film may now be positioned so that the paralleltechnique rather than the bisecting-angle technique can be utilized. Theside wings have flanges 13 protruding into the space between blockportions 4 and 5 and retained there by a snapping action.

It should be observed that the invention has many embodiments differingfrom those here described for exemplifying purposes only. The inventiveidea resides in the realization that the bite block should be arrangedso that its cross-section may vary between substantially rectangular andsubstantially wedge-shaped form, the corresponding principle beingillustrated in FIG. 2. There are several other ways in which such adeformation may be obtained. It should especially be pointed out thatthe "axis" around which portions 4 and 5 turn does not have to be aconcrete portion of the instrument. Any bite block which is deformableas above described falls within the scope of the invention.

The bite block may, in a manner known per se, be provided with markingsmaking it possible for the dentist (by reference to one or more teeth)to ascertain that upon repeated X-raying of one and the same portion ofthe jaw the film will always assume the same position so that allexposures become completely mutually comparable.

I claim:
 1. In a dental instrument for positioning of an X-ray film forX-raying of teeth or adjacent tissues, said dental instrument comprisingan X-ray film support, a bite block integral with said film support andextending to one side thereof and generally perpendicular thereto to theplane of the X-ray film supported thereby, and an alignment rod coupledto said bite block for adjusting the position of the bite block relativeto the film support, the improvement wherein said bite blockcomprises:upper and lower flat plate portions spaced from each other,forming a gap, one of said portions being integral with said filmsupport extending outwardly therefrom and generally perpendicular to theplane of the X-ray film, the other portion being generally parallel tosaid one portion, and means for pivotably connecting said upper andlower plate portions at said gap for pivoting about an axisperpendicular to the plane of the X-ray film, and the plane of bitedefined by the tooth rows contacting the top of the upper plate portionand the bottom of the lower plate portion of the bite block, and whereinthe plate portion of said bite block not integral with the film support,is free of said other portion except at said pivot connectiontherebetween, permitting the two plate portions to automatically assumesuch angular positions that each of them is parallel with a planethrough the chewing surfaces of the adjacent tooth row to insure thatonce the teeth have been clamped to the bite block plate portions, thebite block and the X-ray film support are securely retained in theposition selected by the dentist.
 2. The dental instrument as claimed inclaim 1, wherein said means for pivotably connecting said plate portionsof said bite block comprises an integral bridge extendingperpendicularly to the X-ray film support, centered within said gapseparating said upper and lower plate portions.
 3. The dental instrumentas claimed in claim 2, further comprising a rotatable sleeve connectedto said bite block at the end of said bridge, remote from said filmsupport, and wherein said alignment rod is connected to said sleeve forrotation of said sleeve about its axis and coaxially of said bridge. 4.The dental instrument as claimed in claim 1, wherein said means forpivotably connecting said upper plate portion of said bite block to saidlower plate portion comprises a cylindrical sleeve connected at one endto said upper and lower bite block plate portions, maintaining saidplate portions normally coplanar and separated from each other, andwherein said alignment rod is coupled to said rotatable sleeve at itsend remote from said bite block plate portions.
 5. The dental instrumentas claimed in claim 4, wherein said rotatable sleeve is slidably mountedat said one end to the ends of said bite block upper and lower plateportions remote from said X-ray film support for movement parallel tothe X-ray film support, such that the pivot axis between said upper andlower plate portions may be variably set throughout the width of saidbite block.
 6. The dental instrument as claimed in claim 1, furthercomprising a pair of rectangular block form wings, said wings includingflanges projecting from given ends thereof and insertably receivedwithin said gap between said upper and lower bite block plate portionsso as to detachably connect said wings to respective sides of said biteblock for enlarging the bite surface area, as provided by the upper andlower plate portions of the bite block.